The present invention pertains to a hydraulic fluid tank for motor vehicles with a fluid filter.
Such hydraulic fluid tanks are part of the hydraulic system in motor vehicles. The necessary hydraulic pressure is generated by a hydraulic pump. The connection between the individual elements of the hydraulic system is established by means of hydraulic lines. A fluid filter, which is used to filter the fluid flowing back from the servo elements of the motor vehicle, is inserted into the hydraulic fluid tank. Both coarse fibrous filters and fine paper filters, which are used corresponding to the requirements imposed, have been known as fluid filters.
It is necessary to dimension the filter area of the fluid filter such that a sufficient reserve is available at the expectable average contamination of the fluid filter relative to its service life for a maximum dynamic pressure to be exceeded in the hydraulic system, because the clogging of the pores of the fluid filter implies the risk that the dynamic pressure will increase uncontrollably within the hydraulic system, as a result of which the function of individual units may be disturbed or lost altogether.
However, this also means that the size of the fluid filter must increase if a finer filter material is used in order to make available a sufficient reserve filter surface because the finer pores are naturally also clogged by contaminants more rapidly than are coarser ones. Moreover, it must also be guaranteed that the fluid filter is always arranged beneath the fluid level in the hydraulic fluid tank during the operation because it would otherwise draw in air, which may compromise the ability of the units of the motor vehicle to function in the hydraulic system.
The essential requirement that the hydraulic fluid tank accommodating the fluid filter must be increased arises in connection with the above requirement, which is ultimately also of significance in the oblique position of the motor vehicle, and this requirement to increase the size of the fluid filter is disadvantageous not only because the space available for installation in the engine compartment is increasingly smaller, but also because such a hydraulic fluid tank requires a large amount of material and is expensive. The requirements on the fineness of the filter and on the dynamic pressure predetermine the necessary size of the fluid filter and consequently the amount of fluid as well as the size of the hydraulic fluid tank in solutions according to the prior art.
The basic object of the present invention is to provide a hydraulic fluid tank which also permits fine-pored fluid filters to be used at a small size.
This technical object is accomplished according to the present invention with a hydraulic fluid tank for motor vehicles with a fluid filter. The fluid filter is inserted into a filter housing present in the hydraulic fluid tank.
Thus, it is provided that the fluid filter is inserted into a separate filter housing present in the hydraulic fluid tank.
The fluid filter is thus accommodated within the hydraulic fluid tank in a completely encapsulated form. This encapsulation always guarantees that the fluid filter is arranged completely beneath the fluid level built up within the inner filter housing. This is also true with the motor vehicle in an oblique position.
As a result, it also becomes possible to use very fine fluid filter materials because the size of the filter housing can occupy a large part of the interior space of the hydraulic fluid tank and there are only few limitations to the free design of the filter housing.
Thus, it is particularly advantageous to design the filter housing as a two-part housing, which comprises, e.g., an upper part and a lower part, which may be connected to one another by means of a lock-in or snap connection. Other types of connection are, of course, possible as well.
A collar, which is inserted in a firmly seated and sealing manner into a complementary axial flange present in the hydraulic fluid tank, is made in one piece according to the present invention with the outer surface of the lower part of the filter housing accommodating the fluid filter.
The lower bottom of the lower part has, furthermore, an admission opening, through which the hydraulic fluid to be filtered flows into the fluid filter through at least one pressure pipe joint within an admission chamber formed by the axial flange.
Moreover, it is expedient to provide in the lower part of the filter housing at least one outlet opening, through which the filtered hydraulic fluid can flow over into the hydraulic fluid tank.
The hydraulic fluid thus flows over the pressure pipe joint into the admission chamber, then passes through the admission opening of the lower part, is pressed through the fibrous material of the filter and is filtered in the process in order to be subsequently discharged through the outlet opening into the hydraulic fluid tank. It can now be fed into the hydraulic system in the purified form.
According to another embodiment of the present invention, an additional filter material is also provided in the outlet opening.
The fluid filter should be supported within the filter housing against the force of a spring element. The supporting of the fluid filter via a spring element means an additional safety aspect for the entire system, because if the fluid filter were completely clogged, the dynamic pressure present in the entire system would increase disproportionately. This pressure would consequently also affect the interior space of the fluid filter via the pressure pipe joint and the admission chamber, so that there could be a risk of destruction of certain components. The fluid filter would be raised by a small amount in this case in the axial direction against the force of the spring element, so that the fluid can flow under the raised fluid filter in the direction of the outlet opening and thus it can be fed into the entire system.
Thus, this solution describes a bypass, which offers the advantage over pressure relief valves arranged above the fluid filter that dirt particles already present in the fluid filter material cannot be removed from the filter material and cannot be returned into the hydraulic system, because the hydraulic fluid is discharged below the fluid filter.
On the whole, it is guaranteed in a solution according to the present invention because of a first filling under vacuum that the fluid level within the filter housing is always higher than the fluid level in the hydraulic fluid tank.
There is, of course, also a risk that the filter housing is dislodged from its anchoring in the hydraulic fluid tank. To avoid this and thus to limit the axial mobility of the filter housing as a whole, it is propvided, furthermore, that a holding-down device be arranged either on the inner surface of the hydraulic fluid tank or on the outer surface of the upper part of the filter housing, which holding-down device is located at a closely spaced location only from the surface of the corresponding other component, which surface is associated with it in an opposing manner.
The hydraulic fluid tank according to the invention being described here can be manufactured as a whole from plastic in an advantageous manner. It may comprise a plurality of individual parts in the preassembled state, which are connected to one another after the introduction of the filter housing into the hydraulic fluid tank by, e.g., ultrasonic or orbital welding or bonding and thus they ultimately form a one-part component. Other types of connection of the individual parts of the hydraulic fluid tank may, of course, be applied as well instead of the above-mentioned types. What is meant here is, e.g., screw connections or snap connections with the insertion of corresponding sealing elements, etc.
Fibrous, metal or paper filters of a fineness adapted to the needs may be used as filter materials for both the fluid filter and a corresponding insert.
A hydraulic fluid tank according to the present invention has a number of advantages over that known from the prior art.
Due to the encapsulation of the filter housing, a very large filter area can be used. This may correspondingly have a greater pore fineness than is possible in the solutions known from the state of the art. The hydraulic fluid tanks according to the present invention can also be made, on the whole, smaller.
The admission of air into the hydraulic system is nearly ruled out because the fluid filter is always arranged beneath the fluid level as a consequence of the fluid filter in the filter housing being encapsulated. Since the filter housing is a closed, encapsulated system, the fluid level cannot drop by itself within the filter housing. The dynamic pressure can be limited to a predetermined, maximum value, so that the destruction of the system is avoided with a hydraulic fluid tank according to the present invention.
Moreover, the simple design of the bypass used for this prevents particles already filtered out of the hydraulic fluid from being entrained from the fluid filter and from being returned into the system, because the fluid flows under the fluid filter.
Two embodiments of a hydraulic fluid tank according to the present invention will be described in greater detail below with reference to the corresponding drawings.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.